Usage Cronwrapper

Table of Contents

Introduction

The cronwrapper.sh is a script to wrap your (existing) cronjob.

It does a few small and helpful things:

  • The wrapper fetches any output of stdout + stderr and creates a log file with a name based on the started script (remark: you can override the naming with a 3rd parameter). Do not try to keep silent anymore: write as many output as you want! And some more good news: Write the output in your cronscripts that you can understand the execution!
  • The wrapper logs a few things by itself:
    • the started command
    • starting time
    • ending time
    • … and if having them: the execution time
    • the exitcode of the command/ script; This means: be strict like all commands do! Write your cronjob script that ends with exitcode 0 if it is successful and quit with non-zero if any error occurs. Be strict with the exitcode to be able to monitor the cronjobs!
    • The TTL value (parameter 2) generates a file with a timestamp. A check script detects with it if a cronjob log is outdated
  • all metadata and the output will be written in a log file with parsable

Show help

Use -h to show a help:

cronwrapper.sh -h

                                                                           | 
    A  X  E  L  S                                                        --x--
   ______                        ________                                  |
  |      |.----.-----.-----.    |  |  |  |.----.---.-.-----.-----.-----.----.
  |   ---||   _|  _  |     |    |  |  |  ||   _|  _  |  _  |  _  |  -__|   _|
  |______||__| |_____|__|__|    |________||__| |___._|   __|   __|_____|__|  
                                                     |__|  |__|
                                                                       v 2.0

  Puts control and comfort to your cronjobs.

  📄 Source : https://github.com/axelhahn/cronwrapper
  📗 Docs   : https://www.axel-hahn.de/docs/cronwrapper/
  📜 License: GNU GPL 3.0

ERROR: missing parameters.


####| ✨ SYNTAX |####

  ./cronwrapper.sh TTL COMMAND [LABEL]


####| 🏷 PRAMETERS |####

  TTL     integer value in [min]
          This value says how often your cronjob runs. It is used to verify
          if a cronjob is out of date / does not run anymore.
          As a fast help a few values:
            60    - 1 hour
            1440  - 1 day
            10080 - 7 days
  
  COMMAND command to execute
          When using spaces or parameters then quote it.
          Be strict: if your job is ok then exit wit returncode 0.
          If an error occurs exit with returncode <> 0.
  
  LABEL   optional: label to be used as output filename
          If not set it will be detected from basename of executed command.
          When you start a script with different parameters it is highly
          recommended to set the label.


####| 📝 REMARK |####

  You don't need to redirect the output in a cron config file. STDOUT and
  STDERR will be fetched automaticly. 
  It also means: Generate as much output as you want and want to have to debug
  a job in error cases.


####| 🗨 MORE TO SAY |####

  The output directory of all jobs executed by ./cronwrapper.sh is
  /var/tmp/cronlogs.
  The output logs are parseble with simple grep command.

  You can run ./cronstatus.sh to get a list of all cronjobs and 
  its status. Based on its output you can create a check script for your 
  server monitoring.

  You can sync all logfiles of all cronjobs to a defined server using
  ./cronlog-sync.sh

Replace existing Cronjobs

I am sure you already have some cronjobs on your systems :-)

You don’t need to rewrite anything - we add the wrapper only.

As an example … if you have a daily cronjob like this starting at 3:12 am:

7 * * * * root /opt/mybackup/backup.sh >/var/log/cronjobs/my-backup.log 2>&1

To use my wrappper

  • add the wrapper in front
  • add a TTL (in minutes) as first param. It defines how often this job is called. This will let us detect if a job is out of date.
  • add the command as third param - if you use arguments, then you need to quote it
  • optional: add a label for the output file (it overrides the default naming convention of the log)
  • remove the output redirections

The cronjob above needs to be rewritten like that:

12 3 * * * root /opt/cronwrapper/cronwrapper.sh 60 /opt/mybackup/backup.sh "my-backup"

Rewrite an existing cronjob

To test it immediately run the cron command line with its user:

/opt/cronwrapper/cronwrapper.sh 60 /opt/mybackup/backup.sh "my-backup"

You may ask: And what is the difference now? First: your task does the same thing(s) like before.

But we us a wrapper with its functions described on top.

Run cronstatus.sh.

And then have a look to the generated files in /var/tmp/cronlogs/. And the next chapter.